Critical analysis of antifungal susceptibility testing

Yeast infections are an increasingly important problem and the recognition of antifungal resistance stresses the need for improved susceptibility testing, Antifungal susceptibility testing has lacked reproductibility because of the absence of universally accepted guidelines. The major sources of variation in susceptibility testing have been attributed to the choice of medium and pH, inoculum preparation and size, incubation temperature and time, and end-point criteria. These parameters have been addressed by the National Commmittee for Clinical Laboratory Standards (NCCLS) and proposed guidelines have recently been published (M27-P). Although major advances in fungal susceptibility testing have been achieved, the results of studies to date do not support a correlation between the results of in vitro susceptibility testing and in vivo response. Routine antifungal susceptibility testing of yeasts should therefore be discouraged. Susceptibility testing of the filamentous fungi is currently poorly developed.